Standard sized toilet seats are designed to accommodate the body contours of an average adult. They are not well suited to small children, who often must support themselves with their arms to avoid falling through the seat opening. This problem makes the process of toilet training young children all the more difficult.
Large and obese adults often have the opposite problem, as their bottom body contours extend well beyond the rim of the standard toilet seat, making it difficult for them to maintain their balance on the seat.
Attempts to address these problems have included special toilet seat inserts, such as child seats. But small children usually cannot deploy such inserts without adult assistance, which defeats the goal of enabling the child to use the toilet independently.
Another approach has been tiered toilet seats, in which a smaller seat rests on top of a larger seat, and the two seats are cooperatively hinged. But such tiered seat configurations tend to raise the overall height of the seat, making the seating of small children and infirm adults even more difficult. Moreover, the overlapping edges of tiered toilet seats tend to generate lateral movement of the seats when bearing bodily weight, thereby making seating more unstable and less comfortable.
The cross-sectional profile of the standard toilet seat is typically flat to slightly convex, which is not optimal for stable seating. Smaller adults and children tend to fall inward on the seat, while larger adults slide outward. Aged and infirm adults often require assistance maintaining their seating on these seats, because they provide no lateral support.
(Note: As used in the following descriptions and claims, the terms “outer”, “outward” or “outwardly” refer to the horizontal direction toward the perimeter of the toilet bowl, while the terms “inner”, “inward” or “inwardly” refer to the horizontal direction toward the center of the toilet bowl. The terms “upper”, “upward” or “upwardly” refer to the vertical direction opposite the base of the toilet bowl, while the terms “down”, “downward” or “downwardly” refer to the vertical direction toward the base of the toilet bowl. The term “above” means relatively upward, while the term “below” means relatively downward. The term “top” refers to the most upward, while the term “bottom” refers to the most downward. The term “inclining” means upwardly curving, while the term “declining” means downwardly curving.)